simplify the bug report template (#63851)

* simplify the bug report template

Changes involve:
- Merging how to reproduce and what happened as these two pieces of information are naturally intertwined and a good reproduction walkthrough usually tells the story of what went wrong along the way.
- apache airflow version is usually a handy information while filing the bug. Instead of giving dropdowns, the user let to mention the airflow version would cover redundant ask of filling the version if it belongs to 3x versions.

* pre-commit fixes

updating the missing line in the bug template

fixing yaml linting issues

* simplify the bug report template

Changes involve:
- Merging how to reproduce and what happened as these two pieces of information are naturally intertwined and a good reproduction walkthrough usually tells the story of what went wrong along the way.
- apache airflow version is usually a handy information while filing the bug. Instead of giving dropdowns, the user let to mention the airflow version would cover redundant ask of filling the version if it belongs to 3x versions.

* pre-commit fixes

updating the missing line in the bug template

fixing yaml linting issues

* reverting linting changes unrelated to the template edit

* add placeholder and update terminology

* retain the airflow version type and structure

Since the issue template is static in nature, hiding the other versions is not allowed.
Retaining the current element type till the alternate options are decided

* add placeholder text for airflow version input and update verbiage.

- updated the airflow version field to have placeholder that hints the reporter run the airflow version command and paste the output.
- minor verbiage update for issue description

* remove quotes for the placeholder